pyqt5 border apply only to parent widget problem

Question

Everyone. I have strange issue in pyqt5. I tried to change border but failed, I have always headache when applying border style. Here comes my code. Pls help me

from PyQt5.QtWidgets import QWidget,QApplication,QTextEdit
from PyQt5.QtCore import Qt
from PyQt5 import QtWidgets
import sys



class SomeWidget(QWidget):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.setStyleSheet('border:10px solid green')
        pass

class mainWidget(QWidget):
    def __init__(self,**kwargs):
        super().__init__(**kwargs)
        widget = SomeWidget(self)
        widget.setWindowFlags(Qt.FramelessWindowHint|Qt.Window)
        widget.resize(self.width()//2,self.height()//2)
        
        widget.show()
        # self.setStyleSheet(styles)
        pass

def test1():
    return 0,1

if __name__ == "__main__":

    app = QApplication(sys.argv)
    mw = mainWidget()
    mw.show()
    sys.exit(app.exec_())
    
    pass

Answer 1

Try it:

import sys
from PyQt5.QtWidgets import QWidget, QApplication, QTextEdit
from PyQt5.QtCore import Qt
from PyQt5.Qt import *


class SomeWidget(QWidget):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        
#        self.setStyleSheet('background: #0ff; border: 10px solid green')
        
        self.widget = QWidget(self)
        self.widget.setObjectName('Custom_Widget')
        self.widget.setStyleSheet('''
            QWidget#Custom_Widget {
                background: rgba( 255, 155, 155, 170);
                border-radius: 20px;
                border: 10px solid green;                   
            }
        ''')

        self.v = QVBoxLayout(self)
        self.v.setContentsMargins(0, 0, 0, 0)
        self.v.addWidget(self.widget)


class MainWidget(QWidget):
    def __init__(self,**kwargs):
        super().__init__(**kwargs)
        widget = SomeWidget(self)
        widget.setWindowFlags(Qt.FramelessWindowHint | Qt.Window)
        widget.setAttribute(Qt.WA_TranslucentBackground)                # +++
        widget.resize(self.width()//2, self.height()//2)
        
        widget.move(100, 100)                                           # +++
        widget.show()
        
        self.setStyleSheet('background:#00f;')


def test1():     # ???
    return 0,1

if __name__ == "__main__":
    app = QApplication(sys.argv)
    mw = MainWidget()
    mw.show()
    sys.exit(app.exec_())

Answer 2

The issue here is that the QWidget class does not support the border property (see this answer and the Qt stylesheet documentation directly).

That being said, changing the QWidget to a QFrame does the trick:

import sys

from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QWidget, QApplication, QFrame


class SomeWidget(QFrame):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.setStyleSheet('border:10px solid green')


class mainWidget(QWidget):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        widget = SomeWidget(self)
        widget.setWindowFlags(Qt.FramelessWindowHint | Qt.Window)
        widget.resize(self.width() // 2, self.height() // 2)

        widget.show()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    mw = mainWidget()
    mw.show()

    sys.exit(app.exec_())